The objective of this research is to determine whether hormones modulate memory storage processes. Considerable evidence suggests that acquisition or performance of a learned response may be influenced by hormones injected just prior to training or testing. However, because the injected hormones can act during performance, factors which may affect performance directly (e.g., motivational, arousal or perceptual effects) may influence acquisition and performance indirectly. In the experiments outlined in this proposal, animals will receive hormone injections at various times after training. Retention will be measured at least 24 hours later. If the treatments modulate memory storage processes, the effectiveness of the treatment should decrease with time after training. Recently, we obtained preliminary evidence that posttrial hormone injections facilitate memory storage processes. In these studies animals received injections shortly after training on a one-trial inhibitory avoidance task. At some doses, animals showed improved retention performance when tested the next day. These results represent the first demonstration of memory facilitation with posttrial administration of hormones. These findings are consistent with the general hypothesis that hormones facilitate memory by establishing a brain state optimal for memory storage. It may be that memory consolidation involves modulation of memory processes by nonspecific physiological consequences of an experience. A significant nonspecific response may promote the permanent storage of the recent events which initiated the nonspecific response. Using posttrial injections, the present research proposal will a) examine the effects on memory of several hormones, b) examine task and species generality, and initiate an analysis of c) the neurobiological basis underlying the phenomenon.